In a biased sample, one or more parts of the population are favored
over others. Two ways to pick a biased sample are listed below.Biased SamplesType Description Example
Convenience
SampleA convenience sample
consists of members of
a population that are
easily accessed.To represent all the
students attending a
school, the principal
surveys the students in one
math class.
Voluntary
Response
SampleA voluntary response
sample involves only those
who want to participate in
the sampling.Students at a school who
wish to express their
opinions complete an
online survey.(^) Determine Validity of Conclusions
Determine whether each conclusion is valid. Justify your answer.
Every tenth person who walks into a department store is
surveyed to determine his or her music preference. Out of
150 customers, 70 stated that they prefer rock music. The manager
concludes that about half of all customers prefer rock music.
Since the population is every tenth customer of a department
store, the sample is an unbiased, systematic random sample. The
conclusion is valid.
The customers of a music store are surveyed to determine their
favorite leisure time activity. Of these, 85% said that they like to
listen to music, so the store manager concludes that most people
prefer to listen to music in their leisure time.
The customers of a music store probably like to listen to music in
their leisure time. The sample is a biased, convenience sample
since all of the people surveyed are in one specific location. The
conclusion is not valid.
a. A radio station asks its listeners to indicate their preference for
one of two candidates in an upcoming election. Seventy-two
percent of the listeners who responded preferred candidate A,
so the radio station announced that candidate A would win the
election. Is the conclusion valid? Justify your answer.
Everyday Use
Bias a tendency or
prejudice
Math Use
Bias error introduced by
selecting or encouraging a
specific outcome
Lesson 3F Predictions 473
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